question about back graduations

[Arnold Schnitzer]

Ken, I hope you are not comparing flat-backs to round-backs, because the bracing on flat-backs makes them a whole different animal. I assume the O.P. was discussing rounds. Am I mistaken? My experience as a maker tells me that harder wood on the back and sides usually relates to a brighter sound, softer wood to a more mellow sound. I don't notice a difference in projection.